The present invention relates to a fire extinguishing system comprising a high pressure liquid accumulator unit and a pump unit, whereby the high pressure liquid accumulator unit comprises at least one liquid bottle for extinguishing liquid, which liquid bottle is connected to a gas source through a gas supply line and comprises an inlet aperture for reception of gas from the gas source, and the pump unit comprises a pump and driving means for driving the pump, whereby a line for feeding extinguishing liquid extends from the liquid bottle in order to provide spray heads with extinguishing liquid and the pump is connected to the liquid bottle through a supply line in order to be able to provide the liquid bottle with liquid. Such a fire extinguishing system is known from the international application with the publication number WO 95/07116.
Using hydraulic accumulators for delivering extinguishing medium has become more and more usual in the fire extinguishing technique. The hydraulic accumulator or accumulators are included in a high pressure liquid accumulator unit, the purpose of which is to deliver extinguishing liquid at high pressure to spray heads or sprinklers. One way of implementing a high pressure liquid accumulator is to connect a gas source to a liquid bottle containing extinguishing liquid, e.g. water. The gas source hereby generates a high pressure in the liquid bottle and presses extinguishing liquid out of the liquid bottle. The gas source consists of a nitrogen bottle, for instance.
It is of great significance for fire extinction that the extinguishing liquid has the right consistency and composition to be able to operate effectively at fire fighting. It is often essential that the drop size of the extinguishing liquid is very small in order that the extinguishing liquid may work effectively. In certain situations and environments, it is important that extinguishing liquid can be shot at high pressure several times.
When high pressure gas bottles are used for pressing extinguishing liquid out of liquid bottles, the extinguishing liquid is strongly cooled when it leaves the liquid bottle. In consequence of the extinguishing liquid being cooled, the whole system can be choked up so that no extinguishing medium can be delivered to the spray heads. Even if the system is not choked up, a negative effect is created in any case because of the fact that when the pressure gas is cooled, its force to drive out extinguishing liquid decreases, which can be fatal for the extinction.